Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$230.81	7.730%	$248.6516	$248.65	$248.65	$248.70
Purchase #2	$105.95	10.103%	$116.6541	$116.65	$116.65	$116.70
Purchase #3	$200.47	5.197%	$210.8884	$210.89	$210.90	$210.90
Purchase #4	$41.25	3.136%	$42.5436	$42.54	$42.55	$42.50
Purchase #5	$67.85	7.757%	$73.1131	$73.11	$73.10	$73.10
Purchase #6	$150.94	3.644%	$156.4403	$156.44	$156.45	$156.40
Purchase #7	$79.56	13.702%	$90.4613	$90.46	$90.45	$90.50
7 purchase totals =	$876.83		$938.7524	$938.74	$938.75	$938.80